Conventionally, an unbalance correction method is known for correcting the unbalance of, for example, a rotor as disclosed in Patent Document 1, the rotor being included in a turbocharger to be installed in an engine of an automobile or the like and being configured to rotate by using exhaust gas from the engine as a power source.
Here, a typical turbocharger 100 is illustrated in FIG. 8.
The turbocharger 100 is configured to compress and supercharge supplied intake air into the engine, which increases power and improve efficiency of the engine. The rotor 101 rotates at an extremely high speed during the supercharging.
Such a turbocharger 100 generates excessive vibrations through the rotation of the rotor 101 if a large unbalance exists in the rotor 101, which may cause problems such as vibrations of portions that support the rotor 101 and noise resulting from the vibrations. Thus, for the turbocharger 100, the balance of the rotor 101 is extremely important. Here, in the manufacturing process of the turbocharger 100, for example, an unbalance of the rotor is corrected in a short period of time without disassembling the turbocharger 100, using a configuration in which torque is applied to the rotor 101.
Conventionally, in correcting the unbalance of the turbocharger, air which simulates the exhaust gas from the engine is used to rotate the rotor at predetermined operating speed. In a state in which the rotor is rotating, vibrational accelerations are detected by acceleration sensors, and a rotation phase of the rotor is detected by a phase detector. Adjustment of the balance of the rotor (the unbalance correction) is applied to the magnitude and phase of the unbalance of the rotor detected with the vibrational acceleration and rotation phase. Note that the balance adjustment is applied by cutting and removing (by machining or the like) portions of the rotor equal to the unbalance.
In Patent Document 2, for example, a method is disclosed in which a rigid table, on which a high-speed rotating device is mounted, is supported by springs and vibration is measured by load indicators or vibration measuring instruments. In this case, one to two natural frequencies can be set by the table and the springs, which enable steady balance adjustment regardless of any effects from individual variability in casings of respective workpieces.